Investments in Partially Owned Entities (Summary of Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Schedule Of Equity Method Investments
Our share of net income (loss)	$ 33,714	$ 29,073
Fifth Avenue and Times Square JV
Schedule Of Equity Method Investments
Equity method ownership percentage	51.50%
Equity in net income	$ 16,309	9,606
Return on preferred equity, net of our share of the expense	9,226	9,226
Our share of net income (loss)	$ 25,535	18,832
Alexanders Inc
Schedule Of Equity Method Investments
Equity method ownership percentage	32.40%
Equity in net income	$ 4,671	5,729
Management, leasing and development fees	1,020	575
Our share of net income (loss)	5,691	6,304
Partially owned office buildings/land
Schedule Of Equity Method Investments
Our share of net income (loss)	2,477	5,972
Other investments
Schedule Of Equity Method Investments
Our share of net income (loss)	$ 11	$ (2,035)